1. Field of the Invention
The invention relates to a novel and simple method of manufacturing oligo(4-(2-organoorganooxysilylalkyl)cyclohexane-1,2-diyl)bis-oligosulfide s.
2. Discussion of the Background
Sulfur containing organosilanes are used as silane adhesives or strengthening additives in silicate filled rubber mixtures, for applications such as, among others, vehicle tire treads and bodies. Sulfur-containing silane adhesives can also be used in manufacturing sealing compositions, molds for metal casting, colored and protective coatings, adhesives, asphalt mixtures, and silicate filled plastics. There are also possible applications in the area of fixing functional groups and substances to inorganic substrates, in, e.g., immobilizing of enzymes, manufacturing of fixed bed catalysts, and liquid chromatography.
Various methods may be used to produce sulfur-containing organosilicon compounds. Thus, it is known to produce bis(organo-organooxysilyl)oligosulfides, preferably bis(alkylorganooxysilyl)oligosulfides or mercaptoalkylalkoxysilanes, by reacting haloalkyltrialkoxysilanes (particularly halopropyltrialkoxysilanes) with Met.sub.2 S.sub.x and/or MetSH (where Met represents NH.sub.4, Na, or K, and x=1 to 6) (DE-2,141,159 and DE-2,212,239; and U.S. Pat. Nos. 3,978,103 and 4,048,206). In this connection, the polysulfide Met.sub.2 S.sub.x can also be prepared in situ from MetOR (where R represents alkyl or cycloalkyl), MetSH, and S (DE-2,542,534, DE-2,712,966, and DE-3,311,340).
Further, the preparation of bis[(.beta.-trialkoxysilylethyl)benzyl]oligosulfides by reacting .beta.-trialkoxysilylethylbenzyl halides with NaHS and S is known (DE-3,504,241). The reaction of haloalkylalkoxysilanes with S and H.sub.2 S in the presence of an amine or NH.sub.3 to form alkoxysilylalkyl polysulfides has also been described (DE-2,648,241).
Further, mercaptoalkylalkoxysilanes, preferably mercaptopropylalkoxysilanes, can be converted to bis(organoorganooxysilyl)oligosulfides, preferably bis(propylorganooxysilyl)oligosulfides. According to DE-2,141,160, S.sub.z Hal.sub.2 can be used for this (where z=1 to 3, and Hal represents Cl or Br; or according to DE-2,405,758, sulfur can be used.
In these methods it is a disadvantage that one must use special sulfidization agents, e.g. polysulfides or hydrogen sulfide or sulfur halides. In addition, there are undesired reaction products such as metal halides or hydrogen halides, which must be separated out in an additional process step. The use of mercaptosilanes necessitates an additional preliminary process step which is quite costly.
In the reaction of vinylsilanes with S and/or with a mixture of S and H.sub.2 S according to DE-2,056,229, the abovementioned disadvantages are avoided. However, the reaction, which is carried out at 100.degree.-200.degree. C., leads to the desired products only when carried out at elevated pressure and in the presence of a sulfidization catalyst. Further, the free mercapto groups, which are unavoidably produced in a side reaction, substantially reduce the times for pre-vulcanization and vulcanization to completion, as is well known. The consequences of this, in addition to reduced production safety, are inadequate intermixing of the components of the vulcanizate and, ultimately, a rubber with inferior physical and mechanical parameters.